/**
 *create by 2012-08-25 pm 17:48
 *@author hexinglun@gmail.com
 *BASE64 Encode and Decode By UTF-8 unicode
 *可以和java的BASE64编码和解码互相转化
 */
(function(){
  var BASE64_MAPPING = [
    'A','B','C','D','E','F','G','H',
    'I','J','K','L','M','N','O','P',
    'Q','R','S','T','U','V','W','X',
    'Y','Z','a','b','c','d','e','f',
    'g','h','i','j','k','l','m','n',
    'o','p','q','r','s','t','u','v',
    'w','x','y','z','0','1','2','3',
    '4','5','6','7','8','9','+','/'
  ];

  /**
   *ascii convert to binary
   */
  var _toBinary = function(ascii){
    var binary = new Array();
    while(ascii > 0){
      var b = ascii%2;
      ascii = Math.floor(ascii/2);
      binary.push(b);
    }
    /*
     var len = binary.length;
     if(6-len > 0){
     for(var i = 6-len ; i > 0 ; --i){
     binary.push(0);
     }
     }*/
    binary.reverse();
    return binary;
  };

  /**
   *binary convert to decimal
   */
  var _toDecimal  = function(binary){
    var dec = 0;
    var p = 0;
    for(var i = binary.length-1 ; i >= 0 ; --i){
      var b = binary[i];
      if(b == 1){
        dec += Math.pow(2 , p);
      }
      ++p;
    }
    return dec;
  };

  /**
   *unicode convert to utf-8
   */
  var _toUTF8Binary = function(c , binaryArray){
    var mustLen = (8-(c+1)) + ((c-1)*6);
    var fatLen = binaryArray.length;
    var diff = mustLen - fatLen;
    while(--diff >= 0){
      binaryArray.unshift(0);
    }
    var binary = [];
    var _c = c;
    while(--_c >= 0){
      binary.push(1);
    }
    binary.push(0);
    var i = 0 , len = 8 - (c+1);
    for(; i < len ; ++i){
      binary.push(binaryArray[i]);
    }

    for(var j = 0 ; j < c-1 ; ++j){
      binary.push(1);
      binary.push(0);
      var sum = 6;
      while(--sum >= 0){
        binary.push(binaryArray[i++]);
      }
    }
    return binary;
  };

  var __BASE64 = {
    /**
     *BASE64 Encode
     */
    encoder:function(str){
      var base64_Index = [];
      var binaryArray = [];
      for(var i = 0 , len = str.length ; i < len ; ++i){
        var unicode = str.charCodeAt(i);
        var _tmpBinary = _toBinary(unicode);
        if(unicode < 0x80){
          var _tmpdiff = 8 - _tmpBinary.length;
          while(--_tmpdiff >= 0){
            _tmpBinary.unshift(0);
          }
          binaryArray = binaryArray.concat(_tmpBinary);
        }else if(unicode >= 0x80 && unicode <= 0x7FF){
          binaryArray = binaryArray.concat(_toUTF8Binary(2 , _tmpBinary));
        }else if(unicode >= 0x800 && unicode <= 0xFFFF){//UTF-8 3byte
          binaryArray = binaryArray.concat(_toUTF8Binary(3 , _tmpBinary));
        }else if(unicode >= 0x10000 && unicode <= 0x1FFFFF){//UTF-8 4byte
          binaryArray = binaryArray.concat(_toUTF8Binary(4 , _tmpBinary));
        }else if(unicode >= 0x200000 && unicode <= 0x3FFFFFF){//UTF-8 5byte
          binaryArray = binaryArray.concat(_toUTF8Binary(5 , _tmpBinary));
        }else if(unicode >= 4000000 && unicode <= 0x7FFFFFFF){//UTF-8 6byte
          binaryArray = binaryArray.concat(_toUTF8Binary(6 , _tmpBinary));
        }
      }

      var extra_Zero_Count = 0;
      for(var i = 0 , len = binaryArray.length ; i < len ; i+=6){
        var diff = (i+6)-len;
        if(diff == 2){
          extra_Zero_Count = 2;
        }else if(diff == 4){
          extra_Zero_Count = 4;
        }
        //if(extra_Zero_Count > 0){
        //	len += extra_Zero_Count+1;
        //}
        var _tmpExtra_Zero_Count = extra_Zero_Count;
        while(--_tmpExtra_Zero_Count >= 0){
          binaryArray.push(0);
        }
        base64_Index.push(_toDecimal(binaryArray.slice(i , i+6)));
      }

      var base64 = '';
      for(var i = 0 , len = base64_Index.length ; i < len ; ++i){
        base64 += BASE64_MAPPING[base64_Index[i]];
      }

      for(var i = 0 , len = extra_Zero_Count/2 ; i < len ; ++i){
        base64 += '=';
      }
      return base64;
    },
    /**
     *BASE64  Decode for UTF-8
     */
    decoder : function(_base64Str){
      var _len = _base64Str.length;
      var extra_Zero_Count = 0;
      /**
       *计算在进行BASE64编码的时候，补了几个0
       */
      if(_base64Str.charAt(_len-1) == '='){
        //alert(_base64Str.charAt(_len-1));
        //alert(_base64Str.charAt(_len-2));
        if(_base64Str.charAt(_len-2) == '='){//两个等号说明补了4个0
          extra_Zero_Count = 4;
          _base64Str = _base64Str.substring(0 , _len-2);
        }else{//一个等号说明补了2个0
          extra_Zero_Count = 2;
          _base64Str = _base64Str.substring(0 , _len - 1);
        }
      }

      var binaryArray = [];
      for(var i = 0 , len = _base64Str.length; i < len ; ++i){
        var c = _base64Str.charAt(i);
        for(var j = 0 , size = BASE64_MAPPING.length ; j < size ; ++j){
          if(c == BASE64_MAPPING[j]){
            var _tmp = _toBinary(j);
            /*不足6位的补0*/
            var _tmpLen = _tmp.length;
            if(6-_tmpLen > 0){
              for(var k = 6-_tmpLen ; k > 0 ; --k){
                _tmp.unshift(0);
              }
            }
            binaryArray = binaryArray.concat(_tmp);
            break;
          }
        }
      }

      if(extra_Zero_Count > 0){
        binaryArray = binaryArray.slice(0 , binaryArray.length - extra_Zero_Count);
      }

      var unicode = [];
      var unicodeBinary = [];
      for(var i = 0 , len = binaryArray.length ; i < len ; ){
        if(binaryArray[i] == 0){
          unicode=unicode.concat(_toDecimal(binaryArray.slice(i,i+8)));
          i += 8;
        }else{
          var sum = 0;
          while(i < len){
            if(binaryArray[i] == 1){
              ++sum;
            }else{
              break;
            }
            ++i;
          }
          unicodeBinary = unicodeBinary.concat(binaryArray.slice(i+1 , i+8-sum));
          i += 8 - sum;
          while(sum > 1){
            unicodeBinary = unicodeBinary.concat(binaryArray.slice(i+2 , i+8));
            i += 8;
            --sum;
          }
          unicode = unicode.concat(_toDecimal(unicodeBinary));
          unicodeBinary = [];
        }
      }
      return unicode;
    }
  };

  window.BASE64 = __BASE64;
})();
